This invention relates generally to refrigeration systems and, more particularly, to a device for controlling the flow of refrigerant from the high to the low side of the system.
In a centrifugal chiller refrigeration system, liquid refrigerant flows to a lower sump portion of a condenser from which it then must be metered to a cooler as part of the refrigeration cycle. A common approach for accomplishing this metering function has been with the use of a float bulb connected to a guillotine valve. Such an apparatus allows the refrigerant flow to be responsive to the level of liquid refrigerant in the sump and also provides a liquid seal to prevent the flow of gaseous refrigerant to the cooler. Typical of such devices are those shown in U.S. Pat. Nos. 3,365,899 and 3,399,544 assigned to the assignee of the present invention. Although these devices are effective in operation, they are relatively complicated and expensive because of the close tolerances that are required. For the same reason, their reliability is also sometimes less than desired.
Because of the above-mentioned complications, a more prevalent approach in the industry has been the use of a simple fixed orifice to accomplish the metering function. With no moving parts, this design is simple, reliable and effective for the purpose intended. Since the orifice must be sized for a 100 percent load, it is relatively large in size. If the system is operating at part load, then the large sized orifice allows not only liquid refrigerant to pass, but also the gaseous refrigerant. Although this refrigerant gas flow represents a parasitic loss in the system, it has heretofore been tolerated for the sake of simplicity and reliability.
Heretofore the preferred refrigerant for centrifugal chiller refrigeration applications has been R-11. But, because of possible detriment to the environment, there is a movement in the refrigeration industry to use alternative refrigerants in such systems. One of these alternatives is R-22, which operates at higher pressures and is therefore a much more dense refrigerant (i.e. by a factor of 8) and one which provides a substantially reduced refrigeration cycle efficiency. The use of the higher density refrigerant thus becomes significant in a number of aspects with regard to the gas bypass that has been tolerated as discussed hereinabove. Because of the reduced cycle efficiency, the parasitic losses become more critical. Secondly, because the refrigerant is substantially more dense, a given volume of gaseous refrigerant that is bypassed represents a proportionately greater loss. Finally, because of the inherent need for a high pressure machine (i.e. 300 PSI versus 15 PSI), a given volume loss represents, again, a greater proportionate loss than with a low pressure system. For these reasons, the parasitic losses that have heretofore been tolerated are no longer acceptable. But, on the other hand, it is not desirable to return to the relatively complicated types of float bulb valves that were previously used.
It is therefore an object of the present invention to provide an improved refrigerant flow metering apparatus for a centrifugal chiller system.
Another object of the present invention is the provision for a refrigerant flow control device which operates to prevent the bypassing of refrigerant gas.
Yet another object of the present invention is the provision in a centrifugal chiller system for a refrigerant flow control device which is simple and reliable in construction.
Yet another object of the present invention is the provision in a centrifugal chiller system for a refrigerant flow control apparatus which is economical to manufacture and simple and effective in use.
These objects and other features and advantages become more readily apparent upon reference to the following description when taken in conjunction with the appended drawings.